/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;
using Spring.Expressions;

namespace Spring.Validation;

/// <summary>
/// <see cref="IValidator"/> implementation that supports validating collections.
/// </summary>
/// <remarks>
/// <p>
/// This validator will be valid only when all of the validators in the <c>Validators</c>
/// collection are valid for all of the objects in the specified collection.
/// </p>
/// <p>
/// You can specify if you want to validate all of the collection elements regardless of the errors by
/// setting the <see cref="BaseValidatorGroup.FastValidate"/> property to <c>false</c>.
/// </p>
/// <p><b>Note</b>, that <see cref="BaseValidatorGroup.FastValidate"/> defaults to <c>true</c> for this validator type!</p>
/// <p>
/// If you set the <c>IncludeElementErrors</c> property to <c>true</c>,
/// <c>ValidationErrors</c> collection will contain a union of all validation error messages
/// for the contained validators;
/// Otherwise it will contain only error messages that were set for this Validator.
/// </p>
/// </remarks>
/// <author>Damjan Tomic</author>
/// <author>Aleksandar Seovic</author>
public class CollectionValidator : BaseValidatorGroup
{
    private bool includeElementErrors = false;
    private IExpression context;

    /// <summary>
    /// Gets or sets the value that indicates whether to validate all elements of the collection
    /// regardless of the errors.
    /// </summary>
    /// <remarks>This is just an alias for <see cref="BaseValidatorGroup.FastValidate"/> property</remarks>
    public bool ValidateAll
    {
        get { return !base.FastValidate; }
        set { base.FastValidate = !value; }
    }

    /// <summary>
    /// Gets or sets the value that indicates whether to capture all the errors of the specific
    /// elements of the collection
    /// </summary>
    public bool IncludeElementErrors
    {
        get { return includeElementErrors; }
        set { includeElementErrors = value; }
    }

    /// <summary>
    /// Gets or sets the expression that should be used to narrow validation context.
    /// </summary>
    /// <value>The expression that should be used to narrow validation context.</value>
    public IExpression Context
    {
        get { return context; }
        set { context = value; }
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CollectionValidator"/> class.
    /// </summary>
    public CollectionValidator()
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CollectionValidator"/> class.
    /// </summary>
    /// <param name="validateAll">The bool that determines if all elements of the collection should be evaluated.
    /// regardless of the Errors
    /// </param>
    /// <param name="includeElementErrors">The bool that determines whether Validate method should collect
    /// all error messages returned by the item validators</param>
    public CollectionValidator(bool validateAll, bool includeElementErrors)
    {
        this.FastValidate = validateAll;
        this.includeElementErrors = includeElementErrors;
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CollectionValidator"/> class.
    /// </summary>
    /// <param name="when">The expression that determines if this validator should be evaluated.</param>
    /// <param name="validateAll">The bool that determines if this all elements of the collection should be evaluated.
    /// regardless of the Errors
    /// </param>
    /// <param name="includeElementErrors">The bool that determines whether Validate method should collect
    /// all error messages returned by the item validators</param>
    public CollectionValidator(string when, bool validateAll, bool includeElementErrors)
        : this((when != null ? Expression.Parse(when) : null), validateAll, includeElementErrors)
    {
        this.FastValidate = validateAll;
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="CollectionValidator"/> class.
    /// </summary>
    /// <param name="when">The expression that determines if this validator should be evaluated.</param>
    /// <param name="validateAll">The bool that determines if this all elements of the collection should be evaluated.
    /// regardless of the Errors
    /// </param>
    /// <param name="includeElementErrors">The bool that determines whether Validate method should collect
    /// all error messages returned by the item validators</param>
    public CollectionValidator(IExpression when, bool validateAll, bool includeElementErrors)
        : base(when)
    {
        this.FastValidate = validateAll;
        this.includeElementErrors = includeElementErrors;
    }

    /// <summary>
    /// Validates the specified collection of objects.
    /// If the <c>IncludeElementErrors</c> property was set to <c>true</c>,
    /// <paramref name="errors"/> collection will contain a union of all validation error messages
    /// for the contained validators;
    /// Otherwise it will contain only error messages that were set for this Validator.
    /// </summary>
    /// <param name="validationContext">The collection to validate.</param>
    /// <param name="contextParams">Additional context parameters.</param>
    /// <param name="errors"><see cref="ValidationErrors"/> instance to add error messages to.</param>
    /// <returns><c>True</c> if validation was successful, <c>False</c> otherwise.</returns>
    public override bool Validate(object validationContext, IDictionary<string, object> contextParams, IValidationErrors errors)
    {
        if (Context != null)
        {
            validationContext = Context.GetValue(validationContext, contextParams);
        }

        if (!(validationContext is IEnumerable))
        {
            throw new ArgumentException("The type of the object for validation must be subtype of IEnumerable.");
        }

        return base.Validate(validationContext, contextParams, errors);
    }

    /// <summary>
    /// Actual implementation how to validate the specified object.
    /// </summary>
    /// <param name="contextParams">Additional context parameters.</param>
    /// <param name="errors"><see cref="ValidationErrors"/> instance to add error messages to.</param>
    /// <param name="validationContext">The object to validate.</param>
    /// <returns><c>True</c> if validation was successful, <c>False</c> otherwise.</returns>
    protected override bool ValidateGroup(IDictionary<string, object> contextParams, IValidationErrors errors, object validationContext)
    {
        bool valid = true;
        IEnumerable collectionToValidate = (validationContext is IDictionary
            ? ((IDictionary) validationContext).Values
            : (IEnumerable) validationContext);

        // decide whether to pass new validation errors collection
        //(and discard error messages returned by the item validators)
        // OR to pass validation errors collection that was passed to this method
        //(and collect all error messages returned by the item validators)
        IValidationErrors err = (includeElementErrors) ? errors : new ValidationErrors();

        foreach (object objectToValidate in collectionToValidate)
        {
            foreach (IValidator validator in this.Validators)
            {
                valid = validator.Validate(objectToValidate, contextParams, err) && valid;
                if (!valid && this.FastValidate)
                {
                    break;
                }
            }

            if (!valid && this.FastValidate)
            {
                break;
            }
        }

        return valid;
    }
}
